In magnetic disc drives, side track writing may occur when magnetic fields influence the storage media beyond an intended write track. A typical magnetic disc drive is designed to write data to a disc by influencing the disc with a series of magnetic fields that are generated by a disc drive head. The magnetic field is provided through a top pole and a return pole which are located in close proximity to the disc media. The magnetic flux is intended to be channeled through a narrow path between the top pole and the return pole to write a main data track. However, it is difficult to obtain absolute control of the magnetic flux, and at least some undesired flux leakage frequently occurs in many drives. When the magnitude of this flux leakage is large enough, the leakage field can write an additional track, or “side track,” on the media.
Side track writing may be detrimental to data integrity and longevity as well as storage density. When a side track writes near or over a previously written main track, the integrity of that track may be jeopardized. This may be particularly true when a main track is subjected to multiple side track writings. Over time, the main track may degrade from multiple over-writes, even if the side track effect is weak.
Side track writing may also compromise storage density on the media. One way to increase storage density is to make data tracks narrower to permit an increased number of adjacent tracks to be written to a disk. However, the presence of side track writing may constrain the extent to which track density can be increased, in part because a narrower data track may be more vulnerable to side track writing.
Various methods have been proposed to reduce side writing. For example, various pole tip shapes have been proposed, including an hourglass shaped pole tip, a head having a tapered pedestal that separates the top pole, “I” shaped pole. The variations in pole shape geometry may reduce the opportunity for leakage fields to write side tracks on the media. However, varying the pole tip shape does not necessarily eliminate side track writing.
Improved methods and systems for reducing side track writing are needed.